1. Field of the Invention
The present invention relates to a semiconductor integrated circuit (referred to as an IC hereinafter) device having an improved package structure and, more particularly, to an IC device having an improved structure for assembling a semiconductor IC chip in a package.
2. Description of the Prior Art
FIG. 1 is a schematic cross-sectional view of a conventional IC device as an example of a package structure of this type, in which a semiconductor IC chip 41 is fixed onto a inside bottom surface of a ceramic package 42 by an adhesive such as an eutectic solder or an epoxy resin.
The package 42 has a plurality of inner or internal electrodes 43 each connected by bonding to one or two of bonding pads of the IC chip 41 through a metallic capillary wire 44. Each of the internal electrodes 48 is also connected electrically to corresponding one of external terminals 46 such as pin grids of the package 42 by use of internal metallic interconnection included in the package 42.
In a fabrication step for packaging of IC device, after the inner electrodes 43 are connected with the bonding pads of the IC chip 41, the package container 42 is sealed with a metallic cap 45 on a sealing post 47 by using a welding technology such as resistance or arch welding or by using an eutectic solderring technology such as a tin-gold alloy solderring so as to protect the semiconductor chip 41.
In an IC package structure as described above, the layout of the internal electrodes 43 is restricted by a layout of bonding pads formed in the IC chip 41 as well as a length of the metallic capillary wire which can be safely connected between the bonding pads and the internal electrodes without contacting with any other conductor.
Recently, families and varieties of semiconductor chips have a tendency to increase every year, which makes it necessary to start a new packaging design when a design change in a layout of bonding pads is desired in the semiconductor IC chip. Furthermore, it is also necessary to develop a new package at each time when a dimensional change of an IC chip 41 such as shown in FIG. 1 is required, even if a layout of the bonding pads stays same.
Consequently, the number of and expenses in development of new packages increase and varieties of packaging species increase so that cost of the IC device rises. Moreover, even a small number of ceramic packages in a stock induced by a slight fluctuation in production quantity will sum up to a large amount in stock money because of a high unit cost of the ceramic package.
Besides, the dimension of the package limits the size of an IC chip to be assembled in the package partly because a metallic capillary wire for connecting the IC bonding pads to the internal electrodes 43 contacts with an inner fringe 47 of the package 42. Although an enlargement in the external dimension of the package may solve those problems, large packages reduce a mounting density of IC packages.